Spontaneous lumbar curve coronal correction after selective anterior or posterior thoracic fusion in adolescent idiopathic scoliosis

Study Design. Retrospective review of anterior and posterior fusions for tr eatment of adolescent idiopathic thoracic scoliosis. Objectives. To evaluate both the instrumented thoracic and the spontaneous lumbar curve corrections after treatment of the primary thoracic scoliosis by either anterior or posterior fusion. Summary of Background Data. Recent reports of thoracic scoliosis fusions ha ve concentrated on the thoracic correction obtained by posterior segmental instrumentation systems. Coronal decompensation occurring because of cu rye progression with imbalance of the unfused lumbar spine has also been inves tigated. No report comparing spontaneous lumbar curve response after select ive anterior versus posterior thoracic scoliosis fusions are available. Methods. One hundred twenty-three cases of primary thoracic-compensatory lu mbar adolescent idiopathic scoliosis were treated by selective thoracic ins trumentation and fusion with either an anterior (n = 70) or posterior (n = 53) Single approach. Thoracic and lumbar Cobb measurements and lumbar apica l translation parameters were assessed before surgery, 1 week after surgery , and 2 years after surgery on upright coronal radiographs. All patients ha d a minimum 2-year follow-up. Results. At 2-year follow-up, the percentage of thoracic curve correction w as superior for the anterior (58%) versus the posterior (38%) group (P < 0. 05), whereas the spontaneous lumbar curve correction was also superior for the anterior (56%) group versus the posterior (37%) group for all curve typ es investigated (P < 0.05). Both treatment groups consistently improved lum bar apical positioning after the thoracic fusion procedure. Conclusions. Spontaneous lumbar curve correction occurs consistently after both selective anterior and posterior thoracic fusion implying intrinsic ab ility of the lumbar spine to follow thoracic spine correction. In the curre nt study, using multisegmented hook-rod systems posteriorly with intentiona l limitation of posterior thoracic correction to avoid decompensation, inst rumented thoracic and spontaneous lumbar curve correction was statistically better after anterior thoracic instrumentation and fusion, with the result s most dramatic for lumbar curve Type C (true King II curves).